"The comic's central character is an ex-Mafia hitman named Jackie Estacado, he joined the mob at 16 and enjoyed the life of sex and violence. However, when he turned 21 his dark powers awakened, and he learned of his evil inheritance. With his special powers, known as the Darkness, Jackie can create anything he desires, but it will crumble to dust at dawn. Jackie's powers are quite deadly, he can use the Darkness to call fourth minions from Hell to aid him, and even survive gunshots. He also uses his powers to maul/feed on people (think of it as a meaner Venom suit).
If he impregnates a woman, the child will inherit his gifts, but will only display the Darkness untill he is the age of 21 (all holders of the Darkness are male, as this is the way the powers are passed on from generation to generation), and Jackie will die, this fact results in Jackie being forced to refrain from sex to his major frustration. Jackie's Powers do not display untill it is dark, but Jackie can also manipulate this by creating his own shadow's/darkness e.g Smoke Grenades, basements."
make this fight at night and no godlike spawn who would win in a way this other dude is extremly powerful but with big limitations you also forget the darkness is immortal is he not?
In Hell, when Spawn became ruler, he was invulnerable as well. And Omnipotent. He was only tricked into giving up the throne.
King Spawn is invulnerable and can pretty much do whatever the hell he wants to, including create sunlight, or whatever it takes to beat The Darkness. Of course, since The Darkness is in Hell, if he's beaten or dies, his soul is now in Spawn's possession.
The Darkness on the other hand wouldn't be quite omnipotent now would he? Even if he were "invulnerable".
Spawn in general has no weakness other than heavenly fire and the Seraph Huntress lances which let out some sort of energy which is supposed to destroy anything made out of necroplasm (made especially to fight Hellspawns). He was hit by one of those lances which was fully charged up and survived (no one else had done so before). He was hit numerous (at least 5) times by heavenly fire when the redeemer first came looking for him. The end result was Spawn killing Redeemer. So normal Spawn doesn't really have any weakness.
King Spawn is without a doubt COMPLETELY without any weakness. Only way to defeat him is to trick him somehow. Cogliostro did it by convincing him to recreate hell (yes, he completely remade an entire realm in a few seconds) and while he wasn't paying attention steal the throne.
As for who is stronger.......like i said, i don't know much about The Darkness, but i'm willing to bet Spawn has both more raw power AND more versatility.